Known coloring materials that use violet pigment dioxazine derivatives similar to the present invention include the materials described below.
Patent Document 1 reports that a blue pigment dispersion including, as essential components, a dioxazine sulfonic acid derivative different from the polyoxyalkylene sulfamoyl compound of the present invention and a cationic comb-shaped graft polymer is able to be finely dispersed and exhibits a large Newtonian flow property. However, when a blue pigment obtained using this method is used for a color filter, the required values for the required brightness, the contrast, and the transmittance haze and the like tend to be unsatisfactory, and the targeted levels are unable to be reached.
Patent Document 2 reports that a polyoxyalkylene-modified phthalocyanine-based colorant is useful as a colorant for thermosetting resins and polyolefin-based materials. In this document, the colorant is used for a UV ink, which differs from the use within a color filter described in the present invention. Further, although example 2 describes a dioxazine violet pigment, the dispersant used is a copper phthalocyanine polyoxyalkylene sulfamoyl compound, and differs from the dioxazine sulfamoyl compound of the present invention.
A color filter for a liquid crystal display device includes a red pixel portion, a green pixel portion and a blue pixel portion. Each of these pixel portions has a structure in which a thin film of a synthetic resin containing a dispersed organic pigment is provided on a substrate, wherein red, green and blue organic pigments are used as the organic pigments.
Of these pixel portions, the blue organic pigment used for forming the blue pixel portion generally uses an ε-type copper phthalocyanine pigment (C.I. Pigment Blue 15:6), and if necessary, this pigment may be combined with a small amount of a dioxazine violet organic pigment (C.I. Pigment Violet 23) to regulate the hue.
Organic pigments used in fabricating color filters require completely different properties from pigments used in conventional general-purpose applications, and specifically, require properties that enable the display screen of the liquid crystal display device to be seen clearly (namely, high contrast), or enable the display screen to appear brighter (namely, high brightness). In order to satisfy these types of requirements, finely powdered organic pigments with an average primary particle size of not more than 100 nm are widely used, but color resist inks prepared using finely powdered organic pigments still suffer from problems of fluidity and light transmittance that need to be addressed. For example, when used as an ink for a color filter for a liquid crystal display, problems such as coating irregularities caused by a deterioration in the Newtonian flow property of the ink during spin coating onto the glass substrate, and inadequate light transmittance following pixel formation that results in unsatisfactory levels of brightness and contrast for the filter are drawbacks that remain unresolved.
As described above, the coloring powder composition for a color filter containing a dioxazine sulfamoyl derivative according to the present invention has been unknown until now, and moreover, a pigment dispersion for a color filter prepared by dispersing the coloring powder composition in a medium, and a color filter prepared by using the dispersion for a blue pixel portion have also not been known until now.
[Patent Document 1]    Japanese Unexamined Patent Application, First Publication No. 2006-52410
[Patent Document 2]    Published Japanese Translation No. 2003-531223 of PCT